Purification and characterization of a phosphatase specifically hydrolyzing p-nitrophenyl phosphate from an oral strain of Streptococcus mutans

Hydrolysis of triclosan monophosphate by dental plaque and selected species of oral micro-organisms

Triclosan monophosphate is a phosphorylated derivative of the antimicrobial agent, triclosan. In comparison with triclosan, it is highly soluble in aqueous solutions. It is hypothesized that, within the oral environment, triclosan monophosphate (which may be devoid of antimicrobial activity) will be hydrolyzed into triclosan by the action of microbial phosphatases. The liberated triclosan may then exert antimicrobial activity. To test this hypothesis, we designed experiments to measure the phosphatase activity of plaque and selected species of oral micro-organisms and to demonstrate hydrolysis of triclosan monophosphate. Tests comparing the minimal inhibitory concentration and minimal bactericidal concentration of triclosan and triclosan monophosphate were also undertaken. Dental plaque and the majority of the bacterial strains tested showed phosphatase activity against p-nitrophenyl phosphate which peaked below neutral pH (acid phosphatases) or above neutral pH (alkaline phosphatases). Dental plaque showed the highest levels of alkaline phosphatase (optimum at pH 9.0) and relatively high levels of acid phosphatase (optimum at pH 6.0 to 6.5). Dental plaque and selected species of micro-organisms were all capable of hydrolyzing triclosan monophosphate, albeit at different rates. The minimal inhibitory concentration and minimal bactericidal concentration values for triclosan monophosphate against eight bacterial strains were always considerably higher than the corresponding values for triclosan. Addition of triclosan monophosphate to an established culture (ca. 10(9) cfu/mL) of Capnocytophaga gingivalis growing continuously showed that triclosan monophosphate was rapidly hydrolyzed into triclosan with concomitant loss of total bacterial viability. It is therefore likely that triclosan monophosphate will be broken down into triclosan within the oral environment with concomitant antimicrobial activity.

Cloning and expression of a neutral phosphatase gene from Treponema denticola

We have isolated and characterized a neutral phosphatase gene, phoN, from Treponema denticola ATCC 35405. The gene was isolated from a T. denticola clone bank constructed in the medium-copy-number plasmid vector pMCL19. Subcloning and nucleotide sequencing of the DNA insert from one phosphatase clone, pTph14, revealed that the activity corresponded to an open reading frame consisting of 1,027 bp coding for a 37.9-kDa protein. Hydrophobicity analysis indicated that the protein exhibits some hydrophobic regions. Indeed, partial purification of the phosphatase suggested that the enzyme was membrane associated both in T. denticola and in the Escherichia coli clone. The pH optimum of the enzyme, approximately pH 6.4, indicated that it corresponded to a neutral phosphatase activity from T. denticola. An examination of possible natural substrates for the enzyme suggested that this enzyme hydrolyzes nucleoside di- and triphosphates. Northern (RNA) blot analysis revealed that this phosphatase gene is not likely to be present in an operon structure.

Molecular characterization of a specific p-nitrophenylphosphatase gene, PHO13, and its mapping by chromosome fragmentation in Saccharomyces cerevisiae

The structural gene, PHO13, for the specific p-nitrophenyl phosphatase of Saccharomyces cerevisiae was cloned and its nucleotide sequence determined. The deduced PHO13 protein consists of 312 amino acids and its molecular weight is 34635. The disruption of the PHO13 gene produced no effect on cell growth, sporulation, or viability of ascospores. The PHO13 locus was mapped at 1.9 centimorgans from the HO locus on the left arm of chromosome IV. By chromosome fragmentation, the PHO13 locus was found to be located about 72 kb from the left-hand telomere of chromosome IV and distal to the HO locus.

Effect of chlorhexidine gluconate on acute nonmicrobial inflammation reaction

The effects of chlorhexidine on the appearance of leukocytes and some hydrolytic enzymes were studied in an experimental acute nonmicrobial inflammation reaction caused by implanation of viscose sponge beneath the backskin. The results showed that chlorhexidine gluconate decreased the number of leukocytes in the inflammatory exudate. The drug used had no measurable effect on the distribution of different types of leukocytes. Chlorhexidine has a clear inhibitory effect on the appearance of phosphatases, glycosidases and peptidases. On the other hand the effect on proteinases was small.

The antibacterial action of the various components of the lactoperoxidase system on a cariogenic strain of Streptococcus mutans

Physiological activity of lactoperoxidase and in vivo concentration of thiocyanate ions were shown to be inhibitory against a cariogenic strain of Streptococcus mutans. However, the amount of H2O2 in vivo may be too low for optimum inhibition by lactoperoxidase system. H2O2 alone also inhibited the growth of S mutants to some degree.

Antibacterial effect of salivary peroxidases on a cariogenic strain of Streptococcus mutans

The antibacterial effect of purified human salivary lactoperoxidase on a cariogenic strain of Streptococcus mutans was demonstrated while another oral peroxidase, probably of leukocytic origin, did not affect the growth. Lactoperoxidase was rapidly adsorbed by bacterial cells indicating the necessity of the contact between the enzyme and the cells before inhibition.